>>Dmitry, check out the price of 3rd-party memory as well. sometimes you can save $$$ by buying completely new memory rather than paying Dell's strange prices.
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>Thank you, John. I would be concerned about getting a chip(s) that might not be 100% compatible with a new Dell notebook. On the one hand I do want to save, but on the other hand I would be willing to pay a little more but be spared technical support headaches. Especially when buying a new notebook and trying to maintain the warranty. But thank you for the suggestion.

I agree with John that Dell's prices on add-on memory, over and above their "e-value" configurations are often way too high.

Most consumer equipment is still aimed at running 32-bit consumer OSs, which can only address 4GB RAM max. Some parts of that address space are reserved for hardware, so the effective max RAM you can get for OS + apps in Win32 is ~3.5GB. The last 0.5GB of a 32-bit machine with 4GB RAM is effectively wasted, that's why you see a lot of machines these days supplied with 3GB RAM.

32-bit Windows server OSs can optionally use Physical Address Extension (PAE) to address more than 4GB RAM, but that's a kludge at best, basically obsolete now that 64-bit is widely used.

So, for consumer OSs there is little need to have more than 2 memory slots of 2GB each. These modules are commodity items, so are inexpensive.

4GB memory modules are still expensive because they're low-volume, aimed at the high-end 64-bit workstation and server market. That market is less price-conscious, so suppliers aren't afraid to charge more for it.

One other thing to bear in mind is that some motherboards support "dual-channel" RAM. If both slots in a 2-slot board are populated, you get higher memory bandwidth and performance. So, 2x 2GB dual-channel modules may perform better than a single 4GB module.